The U.S. and Turkey are discussing plans to expand cooperation in order to put greater pressure on Islamic State (IS) militants, said U.S. Secretary of State John Kerry on Monday during a meeting with his Turkish counterpart, Foreign Minister Mevlut Cavusoglu.

"We all have an interest in taking out Daesh, [al] Nusra terrorist organizations as fast as possible and restoring stability to the region," Kerry said, using another name for IS.

Turkey, a NATO ally, is also part of the multi-national coalition that has been battling IS militants in Iraq and Syria.

However, the U.S. and Turkey have been at odds over the U.S. support of Syrian Kurdish militants that Ankara says are aligned with the Kurdistan Worker's Party (PKK), a terrorist group fighting for autonomy in Turkey.

On Monday, Turkish President Recep Tayyip Erdogan said Turkish security forces had captured or killed more than 5,000 Kurdish rebels aligned with the PKK since July.

He commented ahead of a visit to Washington this week to take part in an international nuclear summit.

Another focal point for the U.S. and Turkey is the Syrian refugee crisis. About 2.7 million Syrians have sought refuge in neighboring Turkey.

"Turkey has been doing its best to host some migrants," Cavusoglu said. "We have spent more than $10 billion.”

Earlier Monday, the U.S. announced plans to provide an additional $20 million dollars in aid to help relief organizations assist refugees in Europe and the Middle East.

The State Department said some of that funding would be directed toward relief efforts in Turkey.